1. Field
The present disclosure relates generally to power converters and, more specifically, to programming controllers for switched-mode power converters.
2. Related Art
Due to their small size, good output regulation, high efficiency, safety features, and reliable performance, switched-mode power converters are often used to provide a controlled, regulated power in electronic circuits and appliances. Switched-mode power converters may be used to convert an alternating current (ac) source or a high-voltage direct current (dc) source into a regulated dc source having a desired voltage. Based on the specific application, different types of switched-mode power converters with different control methods and different features may be used.
Typically, a switched-mode power converter includes a switching element coupled to an energy transfer element. Common examples of energy transfer elements include a transformer or coupled inductor, where electrical energy received by an input winding on the input side is stored as magnetic energy that may be converted back to electrical energy at the output side. Switched-mode power converters typically include a controller for directing the switching element to be switched between an ON state and an OFF state to control the amount of power transferred through the energy transfer element to achieve output regulation and maintain properties of the output between predefined threshold values. For instance, the controller may be implemented in an integrated circuit (IC) having multiple input and output IC terminals that are configured to receive signals representing information sensed and received from different nodes of the switched-mode power converter. By processing the sensed/received signals, the controller may generate control signals to control the switching element to regulate the output of the power converter. For example, the controller may receive a feedback signal representative of the output voltage and/or current of the power converter and an input sense signal representative of the amplitude, zero-crossing, or frequency of the input voltage. Signals used for protection and selecting a mode of operation may also be received by the controller. Based on these signals, the controller may adjust the switching characteristics (e.g., duty cycle, frequency, etc.) of the switching element or may change the threshold band gaps, the current limit threshold, or the mode of operation to vary the performance of the power converter to control the amount of power transferred to the output of the power converter.
To reduce the design time and manufacturing cost required to provide controllers having customized parameters suitable for a wide range of applications, controllers often have parameters that are designed to be trimmed or programmed based on the application environment and/or customer requirements. For example, U.S. Pat. No. 6,388,853 describes programming a parameter of a controller parameter by injecting signals directly into the terminals of the controller. While controller parameters can be effectively programmed in this way, direct access to the controller terminals is required. As a result, the controller can only be programmed prior to manufacturing and board assembly.